This covers multiple fronts. What if the Japanese had shared the design of the Long Lance torpedo with the Germans and the Italians early enough for those designs to be useful? The Long Lance in the Med used by the Italians agains the Brit fleet, especially if the Japanese provided advisors on night torpedo attacks. That might have devastated the RN. In the hand of the Kreigsmarine, couple the Long Lance with homing technology. Maybe the U-Boat kill rates might have been higher. More than developing jet fighters, this is a weapon that really might have had an effect.
I sent a PM asking him to add to his post to include his insight, etc and resubmit it. If he does so, we can approve it.
